Description
Lithium bromide (LiBr) is the chemical compound of lithium and bromine. It has extreme hygroscopic, making it a suitable desiccant in the air conditioning systems. It can also be used in absorption chilling together with water. It is also useful in the organic synthesis such as forming adduct with some pharmaceuticals. In medical fields, it can be used as a sedative and used for the treatment of bipolar disorder. It can be manufactured by the treatment of lithium carbonate with hydrobromic acid.
Physical properties
Lithium bromide is a white, crystalline, deliquescent solid. Aqueous solutions of lithium bromide have unusually low water vapor pressures. The following hydrates are formed: LiBr·H2O, LiBr-2H2O, LiBr-3H2O and LiBr-5H2O. All hydrates have incongruent melting points. Concentrated aqueous solutions of lithium bromide can dissolve significant quantities of polar organic substances such as cellulose. Lithium bromide, like lithium chloride, is soluble in polar organic solvents such as alcohols.
Uses
Lithium bromide is used in absorption, refrigeration and air-conditioning systems. A highly concentrated solution of the salt is an efficient absorbent of water vapor. The vapor pressure of such solution is very low. Other applications include the use of the salt as a swelling agent for wool, hair and other organic fibers; as a catalyst in dehydrohalogenation reactions; and as a sedative and hypnotic in medicine.
Preparation
Lithium bromide is prepared by neutralizing lithium hydroxide or lithium carbonate with an aqueous solution of hydrobromic acid, followed by concentration and crystallization:
LiOH + HBr → LiBr + H
2O
Li
2CO
3 + HBr → LiBr + CO
2 + H
2O
The salt is usually obtained as hydrates. Anhydrous lithium bromide is obtained by heating hydrated salt under vacuum.
Chemical Properties
White cubic crystals; hygroscopic; refractive index 1.784; density 3.464 g/cm3; melts at 550°C; vaporizes at 1,265°C; highly soluble in water (145g/100g at 4°C), much greater solubility in hot water (254g/100g at 90°C); soluble in methanol, ethanol and ether; slightly soluble in pyridine; vapor pressure of aqueous solutions at 52 and 68% concentrations at 25°C are 5 and 0.7 torr, respectively.
Physical properties
White cubic crystals; hygroscopic; refractive index 1.784; density 3.464 g/cm
3; melts at 550°C; vaporizes at 1,265°C; highly soluble in water (145g/100g at 4°C), much greater solubility in hot water (254g/100g at 90°C); soluble in methanol, ethanol and ether; slightly soluble in pyridine; vapor pressure of aqueous solutions at 52 and 68% concentrations at 25°C are 5 and 0.7 torr, respectively.
Uses
As humectant, in air-conditioning systems. An aqueous solution of lithium bromide containing about 50 % lithium bromide is used as an absorbent in large-scale absorption air conditioning equipment. Lithium bromide is also used in limited amounts by the pharmaceutical industry for dehydrobromination of organic compounds to form olefins.
Uses
It is used for reconstitution of brines, as swelling agent for proteins and as electrolyte component in lithium battery. Used as brazing and welding flux. Lithium bromide is used as catalyst for the condensation of carbonyl compounds with active methylene compounds in the absence of solvent, operating medium for air-conditioning and industrial drying system. Also used in manufacturing pharmaceuticals and alkylation process. It also plays an important role in the synthesis of dihydropyrimidinones.
Uses
Lithium Bromide finds use as a desiccant in industrial air conditioning systems and industrial drying agents.
Definition
ChEBI: A lithium salt in which the counterion is bromide. The anhydrous salt forms cubic crystals similar to common salt.
Preparation
Lithium bromide may be prepared by the reaction of lithium hydroxide monohydrate or lithium carbonate with hydrobromic acid. The resultant solution of lithium bromide may be evaporated and cooled to crystallize a hydrate of lithium bromide, the composition of which depends on the final temperature. The lithium bromide hydrate may be filtered from the mixture and carefully dried by the application of heat in a vacuum desiccator to avoid melting the hydrate.
General Description
LiBr/Chlorotrimethylsilane reagent participates in the conversion of alcohols to bromides.
Flammability and Explosibility
Non flammable
Purification Methods
Crystallise it several times from water or EtOH, then dry it under high vacuum for 2 days at room temperature, followed by drying at 100o. Its solubility in H2O is 167% at ~20o, and 250% at ~100o. It is deliquescent and should be stored in a tightly stoppered vessel.
